Logical &#34;or&#34; circuit



April 17, 1962 H. D. CRANE 3,030,520

LOGICAL "OR" CIRCUIT Filed Jan. 20, 1958 h V Il BY Z/f/M jffOR/VESL are United States Patent 3,030,520 LOGICAL R CIRCUIT Hewitt D. Crane, Palo Alto, Calif., assignor to Burroughs Corporation, Detroit, Mich., a corporation' of Michigan Filed Jan. 20, 1958, Ser. No. 710,149 7 Claims. (Cl. 307-88) This invention relates to circuits for performing a logical or function, and more particularly, is concerned with an or function circuit employing magnetic core elements.

In copending application, Serial No. 698,633 filed Novem-ber 25, 1957, now abandoned, in the name of Hewitt D. Crane and assigned to the assignee of the present invention, there is described a core register having -a novel transfer circuit requiring no diodes or other impedance elements in the transfer loops between cores. The basic binary storage element of this circuit is an annular core having an input and output aperture therein. The 4binary zero digits are stored in the form of flux oriented in the same direction in the core on either side of the respective apertures, while the binary one digits are stored in the form of flux extending in opposite directions on either side of the respective apertures. Transfer is eilected by applying a current pulse of predetermined magnitude to a coupling loop linking one aperture in each of two cores, one core constituting a transmitting core and the other core constituting a receiving core.

The present invention utilizes the principles of the above-identied copending application to accomplish the logical or function. According to the present invention, in order to transfer a binary bit to a receiving core, only one of a plurality of transmitting core elements must be set tothe binary one condition.

In brief, the circuit of the present invention comprises a plurality of input or transmitting core elements and a single output or receiving core element. Each of the core elements is made of magnetic material, such as ferrite, having a high flux retentivity, the core elements being annular in shape and having at least two small apertures therein. Each of the core elements is provided with a winding linking the annular core element through one of the apertures, the windings linking the input core elements being connected in series with each other. The winding linking the input aperture of the receiving core element is connected in parallel across the series-connected output windings of the transmitting core elements. Means is provided for applying a transfer pulse across the two parallel paths formed by the series-connected transfer windings linking the transmitting core elements, and the single transfer winding linking the receiving coreelement. The transfer current is controlled ata level slightly less than twice the threshold current required to reverse ux around any one of the annular core elements when in a saturated condition. In this manner, if any one or more of the input core elements is in a set condition, i.e., the output aperture of one or more of the core elements is unblocked so that flux can be switched locally about the output aperture, a ilux change is effected in the receiving core in response to the transfer pulse.

For a better understanding of the invention, reference should `be had to the accompanying drawings wherein:

FIGS. 1 and 2 show a ferrite magnetic core element such as used in the present invention in two conditions of ilux orientation; and

FIG. 3 shows a circuit according to the present invention for providing a logical or function and using the core elements of the type shown in FIGS. 1 and 2.

Consider an annular core, such as indicated at in FIGS. l and 2, made of a magnetic material such as fer- Patented Apr. 17, 1962 rite, having a square hysteresis loop, i.e., a material having a high flux retentivity or remanence. The annular core is preferably provided with two small apertures 12 and 14, each of which divides the annular core into two parallel llux paths as indicated by the arrows. If a large current is pulsed through the central opening in the core l0, as by a clearing winding 16, the ilux in the core may be saturated in a clockwise direction. The core is then said to be in a cleared or binary Zero condition. If a large current is passed through either of the apertures 12 or 14, as by either of the windings 18 and 20, in the direction indicated in FIG. 2, and the current is of suflicient magnitude to cause switching of ilux around the central opening of the annular core, a portion of the tlux can be reversed so that the flux extends in opposite directions on either side of the respective apertures 12 and 14, as indicated by the arrows in FIG. 2. The core is then said to be in the set or binary one state.

The significant aspect of the transfer circuit described in the above-identified copending application is that with a given number of 4turns linking one of the small apertures in the core and with the core in its cleared state as shown in FIG. l, a current exceeding a threshold value It must be provided to change the core to its set state as shown in FIG. 2. If the current does not exceed this threshold level, substantially no ux is switched around the core. The aperture is said to ybe blocked when the current passing through the aperture must exceed the threshold value It in order to switch any flux in the core element.

On the other hand, if the core is already in its set state, a very small current, substantially less than the threshold value It, causes flux to switch locally about the aperture. In this case the aperture is said to be unblocked Thus if a current slightly less than the threshold value current I, is passed through an aperture in a core element, ilux will be switched or not switched Within the core depending upon whether the core is in its cleared state or its set state, i.e., depending on whether the aperture is blocked or unblocked.

This principle is used to provide a circuit producing an or function, the circuit being shown in FIG. 3. This circuit comprises la plurality of input core elements, three being shown by way of example in the ligure, as indicated at 22, 24, and 26. Each of the input core elements is annular in shape and is provided with an input aperture, as indicated at 28, 30, and 32 respectively, the input apertures being linked by input windings, as indicated at 34, 36, and 38 respectively. Each of the input core elements may be cleared by means of a clearing winding 40 which links the central opening of each of the input core elements. A suitable clearing pulse source 4Z is provided 'by means of which the clearing winding 40 can be energized to saturate the llux in each of the input core elements in a clockwise direction, corresponding to the cleared condition as shown in FIG. 1.

Each of the input core elements is further provided with an output aperture, such as indicated 44, 46, and 48 respectively. An output winding links each of the output apertures, as indicated at 50, 52 and 54 respectively. The output windings are connected in series to form part of a transfer loop indicated generally `at 56, which couples each of the input core elements to an output core element 58. The transfer loop includes a winding 60 which links an input aperture 62 in the output core element 58. Thus the transfer loop 56 comprises two parallel branches, one consisting of the seriesconnected windings 50, 52, and 54, and the other branch comprising the winding 60.

The output core element 58 is provided with a clearing winding 64 which links the central opening of the core element 58. The clearing winding is energized from the 'J o suitable clearing pulse source 66. By means of the source 66, the output core element can be cleared with all the flux in the clockwise direction, corresponding to the flux condition shown in FIG. 1.

A transfer current is applied through the two parallel branches of the transfer loop 56 by means of a transfer pulse source. The resistance in the two branches is preferably such that with all of the core elements in the cleared condition, the ampere-turns linking the output apertures of each of the input core elements and the input aperture of the output core element is Vjust below the threshold at which flux begins to switch around the central apertures of the core elements. Thus with all the cores in the cleared state, the pulsing of the transfer loop by the source 68 produces no significant flux change in the core elements.

However, if one or more of the input windings coupled to the input core elements are energized at X, Y or Z by a current sufficient to change the input core elements to the set flux condition, as described in connection with FIG. 2, the associated output aperture is unblocked. If the output aperture is unblocked, this means that flux can be switched locally about the output aperture by a relatively small current. Thus when the transfer pulse is applied `to the loop 6 from a source 68, the resulting current starts to switch flux about the aperture or apertures that are unblocked. This switching of flux about the unblocked aperture or apertures generates a counter which opposes the Iflow of current in the branch of the transfer loop linking the output aperture to the input core elements. As a result, the currentiiowing in the portion of the transfer loop 56 linking the input aperture 62 of the output core element 58 is caused to increase by an amount sucient to exceed the threshold level and thereby causes flux to switch around the central opening of the output core element 53. As a result, the output core element 58 is changed to its set condition.

It will be appreciated that since the windings linking the output apertures of the input core elements are connected in series, if the effective impedance of any one of these windings increases, it is sufficient to divert more current through the winding 60` linking the input aperture of the core 62 of the output core element 58. Thus the or function is accomplished, since with any one of the input core elements in its set condition, the transfer pulse changes the output core element to its set condition.

It is desirable that bias be used on each of the transmitting and receiving cores in order to extend the operating current range of the transfer pulse and to control the threshold level in the receiving core according to the principles set forth in detail in the copending application, Serial No. 704,511, filed December 23, 1957, in the name of Hewitt D. Crane and assigned to the assignee of the present invention. Thus as shown in FIG. 3, bias windings are provided on each of the core elements as indicated at 70, 72, 74 and 76. The bias windings are connected in series with each other and in series with the output of the transfer pulse source 68. One set of turns that has been found to give satisfactory operation is as follows:

Transfer loop windings linking the transmitting cores- 12 turns.

Transfer loop linking the receiving core-1l turns.

Bias windings linking the transmitting cores-1 turn.

Bias windings linking the receiving core- 7 turns.

It should be understood, however, that operation of the or circuit does not depend on the use of bias as such. Moreover, the set of turns listed above is only one example of many sets of turns which are operative.

What is claimed is:

1. A logical or circuit comprising a plurality of input core elements and a single output core element of magnetic material having a high flux remanence, each of the core elements being annular in shape with an input and an output aperture extending through each annular core element, means including windings linking each of the input core elements through the central openings therein provided by their annular shape for clearing all the flux in the input core elements to saturation in one direction, whereby the output aperture of each of the input core elements is blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, whereby the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means including a winding linking the output core element through the central opening therein provided by the annular shape of the core element for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including windings link-` ing each of the input core elements through the output apertures thereof and a winding linking the output core element through the input aperture thereof, the windings linking the input core element being connected in series with each other, the winding linking the output core eleent being connected in parallel with the series connected windings, and means for applying a transfer pulse across the parallel windings of the transfer circuit, the pulse being of a magnitude to produce a total current flow through the transfer circuit equal to slightly less than twice the current required to produce flux reversal in a core element when in a saturated condition as produced by said clearing means.

2. A logical or circuit comprising a plurality of input core elements and a single output core element of magnetic material having a high ux remanence, each of the core elements being annular in shape to provide a large central aperture, with an input and an output aperture extending through each annular core element, means for Y clearing all the flux in the input core elements to satura tion in one direction, whereby the output aperture of each of the input core elements is blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, whereby the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including windings linking each of the input core elements through the output apertures thereof and a winding linking the output core element through the input aperture thereof, the windings linking the input core element being connected in series with each other, the winding linking the output core element being connected in parallel with the series connected -windings, and means for applying a transfer pulse across the parallel windings of the transfer circuit, the pulse being of a magnitude to produce a total current flow through the transfer circuit equal to slightly less than twice the current required to produce flux reversal in a core element vwhen in a saturated condition as produced by said clearlng means.

3. A logical or circuit comprising a plurality of input core elements and a single output core element of magnetic material having a high flux remanence, each of the core elements being annular in shape to provide a large central aperture, with an input and an output aperture extending through each annular core element, means for clearing all the ux in the input core elements to saturation in one direction, whereby the output aperture of each of the input core elements is blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, whereby the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including windings linking each of the input core elements through the output apertures thereof and a winding linking the output core element through the input aperture thereof, the windings linking the input core element being connected in series with each other, the winding linking the output core element being connected in parallel with the series connected windings, and means for applying a transfer pulse across the parallel windings of the transfer circuit.

4. A logical or circuit comprising a plurality of input core elements and a single output core element, each of said core elements being made of magnetic material having a high flux retentivity, the core elements further being annular in shape to provide a large central aperture, and having at least two small apertures therein, each of the core elements having a winding linking the annular core element through one of said apertures, the windings linking the input core elements being connected in series with each other and in parallel with the winding linking the output core element across a pair of terminals, means for applying a transfer pulse between said terminals, the pulse being of a magnitude to produce a total current flow through the two parallel paths across the terminals equal to slightly less than twice the threshold current level required to reverse flux around any one of the annular core elements when in a saturated condition. A

5. A logical or circuit comprising a plurality of input core elements and a single output core element, each of said core elements being made of magnetic material having a high flux retentivity, the core elements further being annular in shape to provide a large central aperture, and having at least two small apertures therein, each of the core elements having a winding linking the annular core element through one of said apertures, the windings linking the input core elements being connected in series with each other and in parallel with the winding linking the output core element across a pair of terminals, and means for applying a transfer pulse between said terminals.

6. An or circuit comprising at least three annular core elements of magnetic material having a square hysteresis characteristic, each of the core elements having a large central aperture and at least a pair of small apertures extending therethrough, one of the core elements being an output element and the remainder of the core elements being input elements, a plurality of input windings, one input winding linking one of the input core elements through one of said pair of small apertures, a plurality of transfer windings, one transfer Winding linking one of the core elements through one of said small apertures, the transfer windings linking the input core elements being connected in series with each other and in parallel with the transfer winding linking the output core element, and means for applying a transfer pulse across the two parallel paths formed by the series-connected transfer windings linking the input core elements and the single transfer Winding linking the output core element, the current level of the transfer pulse being below the threshold required to switch a substantial amount of flux in any of the core elements when they are all saturated with all the flux in one direction.

7. An or circuit comprising at least three annular core elements of magnetic material having a square hysteresis characteristic, each of the core elements having a large central aperture and at least a pair of small apertures extending therethrough, one of the core elements being an output element and the remainder of the core elements being input elements, a plurality of transfer windings, one transfer winding linking one of the core elements through one of said small apertures, the transfer windings linking the input core elements being connected in series with each other and in parallel with the transfer winding linking the output core element, and means for applying a transfer pulse across the two parallel paths formed by the series-connected transfer windings linking the input core elements and the single transfer winding linking the output core element, the current level of the transfer pulse being below the threshold required to switch a substantial amount of ux in any of the core elements when they are all saturated with all the flux in one direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,741,758 Cray Apr. l0, 1956 2,742,632 Whitely Apr. 17, 1956 2,896,194 Crane -luly 21, -9

OTHER REFERENCES Proceeding of the IRE, vol. 44, Issue 3, pp. 321-332, March 1956, by Rajchman and Lo. 

